Dolomite after Calcite with Sphalerite

specimen number:
2312185

location:
Boldut Mine, Cavnic, Maramures Co., Romania

description:

Scalenohedral crystals of what were once calcite to 4.0 cm in size, these now replaced by glistening colorless crystals of dolomite and scattered across the top of matrix with sphalerite and minor calcite. Classic pseudomorph for the species and locality. In excellent condition.

The Boldut Mine, situated in the Cavnic mining district of Maramures County, Romania, is part of a historic polymetallic extraction center with roots dating back centuries. Geologically, the deposit lies within the Neogene volcanic belt of the Eastern Carpathians, where complex hydrothermal vein systems cut through volcanic and sedimentary host rocks. These epithermal solutions deposited rich concentrations of lead, zinc, copper, gold, and silver ores. Beyond its industrial mining history, the Boldut Mine is internationally famous among mineral collectors for producing magnificent specimens of quartz, rhodochrosite, and carbonates in association with various sulfide minerals such as pyrite, sphalerite, and galena.

A pseudomorph occurs when one mineral replaces another while the original crystal shape is preserved. In the case of dolomite after calcite, a crystal of calcite undergoes chemical alteration and replacement by dolomite, resulting in a specimen that possesses the chemical composition of dolomite while retaining the external crystal form and geometry of the original calcite. This fascinating geological process highlights the dynamic nature of mineral stability within hydrothermal or groundwater environments over time.

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